Manufacturing processes in which a material is formed by propelling a fluidized mixture from a nozzle by way of a fluid jet upon which the material solidifies into a desired form are known in the art. For example, spray nozzles are used for spraying liquid paints which can contain pigments, binders, paint additives and solvents, the solvents of which flash or vaporize after the paint is applied to a surface leaving dry paint. Processes for producing fine particles are known in which a mist of a solution is propelled from an atomizing nozzle upon which the solvent flashes or vaporizes leaving the dry particles. While these processes are capable of forming fine, uniform particles, there is no existing process for collecting the particles in a manner that preserves the uniformity of the newly issued particles, owing to the extremely high speed at which they are propelled.
Flash spinning is an example of a spray process having very high issuance speed. Flash spinning processes involve passing a fiber-forming substance in solution with a volatile fluid, referred to herein as a “spin agent,” from a high temperature, high pressure environment into a lower temperature, lower pressure environment, causing the spin agent to be flashed or vaporized, and producing materials such as fibers, fibrils, foams or plexifilamentary film-fibril strands or webs. The temperature at which the material is spun is above the atmospheric boiling point of the spin agent so that the spin agent vaporizes upon issuing from the nozzle, causing the polymer to solidify into fibers, foams or film-fibril strands. Conventional flash spinning processes for forming web layers of plexifilamentary film-fibril strand material are disclosed in U.S. Pat. No. 3,081,519 (Blades et al.), U.S. Pat. No. 3,169,899 (Steuber), and U.S. Pat. No. 3,227,784 (Blades et al.), U.S. Pat. No. 3,851,023 (Brethauer et al.). However, the web layers formed by these conventional flash spinning processes are not entirely uniform.